2Geom: easy 2D graphics library

What is this?

2Geom is a C++ 2D geometry library geared towards robust processing of computational geometry data associated with vector graphics. The primary design consideration is ease of use and clarity. It is dual-licensed under LGPL 2.1 and MPL 1.1.

The library is descended from a set of geometric routines present in Inkscape, a vector graphics editor based around the Scalable Vector Graphics format, the most widespread vector graphics interchange format on the Web and a W3C Recommendation. Due to this legacy, not all parts of the API form a coherent whole (yet).

Rendering is outside the scope of this library, and it is assumed something like libcairo or similar is employed for this. 2geom concentrates on higher level algorithms and geometric computations.

Features List

C++ 17
Functional programming style.
Points
Efficient affine transformations
Rectangles
Convex Hulls
Bounded error
General purpose paths:
- Exact elliptical arcs
- Area
- Centroid and bending moments
Path Locations:
- Determination of special spots (e.g. maximum curvature)
- Splitting
- Point, tangent, curvature at location
- Efficient arc length and inverse arc length
Path algebra:
- Computations such as offset curves can be written with their mathematical definition and still get a bounded error, efficient curve. (preliminary trials indicate offset done this way out performs the method used in Inkscape)
Arbitrary distortion (with bounded error):
- Mesh distorts
- Computational distorts such as the GIMP's 'vortex' plugin
- 3d mapping (perspective, flag, sphere)
Exact boolean ops (elliptic arcs remain elliptic arcs)
Efficient 2d database
Implicit function plotting
NURBs input and output
Tunable path simplification
PDoF constraint system for CAD/CAGD

Dependencies

To build 2Geom, you will need:

C++ 17
Boost (headers only)
glib
GNU Scientific Library
double-conversion
cairo
Ragel (if you want to modify the SVG path parser)
GTK+ 2 (for demo programs)

Building

2Geom uses CMake as the build and configuration system. To build, type:

mkdir build && cd build
cmake ..
make

To run tests and performance tests:

make test
make perf

Note: Tests are disabled by default. To enable tests pass -D2GEOM_TESTING=ON to cmake command.

Also check out some of the interactive programs in src/toys.

Documentation is generated from source comments using Doxygen. Run doxygen in the project root to generate documentation in doc/html.

API / ABI Stability

Version 1.0 of 2Geom marks its first official release. With this release the library's API/ABI is considered stable:

All public APIs will not be renamed or have their parameters changed without providing backwards-compatible aliases.
New functionality added to these APIs will not change their meaning or fundamental behaviors.
If an API needs to be removed or replaced, it will be declared deprecated but will remain in the API until the next major version. Warnings will be issued when the deprecated method is called.
We'll only break backwards compatibility of these APIs if a bug or security hole makes it completely unavoidable.

Improvements that would break the API/ABI will be noted in our bug tracker, for a future release.

2Geom does not follow Semantic Versioning. Instead, version numbers match major Inkscape release versions.

Further information

Communications related to 2Geom development happen on a SourceForge mailing list.

The primary user of 2Geom is Inkscape. API-breaking changes to 2Geom will require corresponding changes to Inkscape.

zhaowenlan1779 / lib2geom